Advanced and improved
traditional welding processes
Venezia Lido, 21 - 22 May 2009
Innovative Applications of Fully
Automated Electron-Beam-Welding for
the Transportation Industry
Dr.-Ing. Christian Vogelei - pro beam AG & Co. KGaA - Planegg -
Dipl.-Ing. Guido Reuter - 1. ISR GmbH - Seekirchen – Austria
Electron beam welding is a rather old process
compared to the laser process. Already in 1949
there were first successful applications using the
energy of the electron beam. These were EB-
welding and EB-drilling. With the discovery of the
"deep welding effect" the EB welding process is
the preferred process for thicker material. Ever
since, continuous development showed the
potential of the EB-process which has been
utilized due to the economical and technological
advantages for more and more applications. The
range today covers work pieces that have tons of
weight, mid size series for the machine building
industry and also mass production for
automotive. This paper will show the working
principles of the present EB-technology followed
by various examples of the aircraft, rail, marine
and automotive industry, which benefit from its
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1. Working Principle of an Electron Beam Welding Machine
The energy source for electron beam welding is the free electron. These are emitted by means of
thermal emission from a tungsten cathode.
Setup of an Electron Beam Generator.
The electrons are emitted from the beam
source. Followed by a series of magnetic coils of
which the focus lens is the most important as it
focuses the beam onto the work piece surface.
Below the focus lens there are deflector coils
that can control the movement of the beam
across the surface of the work piece. The
electron beam generator is controlled by an up
to date CNC, equivalent to modern milling
A strong electrical field between the tungsten cathode and the anode accelerates the electrons.
They accumulate high energy usually between 60keV and 150 keV. This kinetic energy of the
electrons is converted into heat when the electrons hit the work piece. This process takes place in
vacuum as the movement of electrons would be diverted as soon as they collide with any gas
molecule. A widened beam of electrons would not have enough energy and energy density to
perform welding. The work piece is mounted on a CNC controlled table that takes care of the
necessary movements. Today's machines offer lock load systems (Pic. 2) to handle the transport
into and out of the vacuum chamber. Thus, the required vacuum does not cause any non
Left: Lock Load Shuttle Machine Right: Lock Cycle Machine
1.1. Positioning and Welding with the Same Tool
When electrons hit the surface of the work piece some of them are rejected due to the physical
Coulomb effect with almost unchanged energy levels. The so called rejected electrons can be
detected by a special sensor. The analysis of the sensor signal reveals information about the
surface of the work piece. Similar like electron microscopes do state of the art electron beam
welding machines utilize this information for automation purposes.
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Application of rejected electrons for visualization
a) shows pictures of the identical work piece, on the left taken by a regular light optical camera with usual light
reflections, whereas the right is the much clearer electron-optical picture.
b) shows the contrast given by the two different materials used to make an EURO coin. The contrast between
the different materials is easy to distinguish. The different metal atoms of the two alloys result in different power
of the coulomb effect. This makes it possible to use the electron optical visualization for automation purposes
The mentioned possibilities to create a clear picture offer a wide potential for automated welding
processes. Modern electron beam welding machines use the visualization to measure and position
the joint of the work piece. Automated joint detection makes the process fully automated without
any manual interaction necessary.
Application of visualization and image processing in modern EB-Welding machine.
For this work piece two tubes have to be welded into the body. With the image processing of the electron optical
image the center of the two tube is automatically identified. This has been of mayor interest for the manufacturer
as the cost for a defined positioning of the work piece could be avoided.
Utilizing an identical tool, the electron beam, for measurement and position as well as for the core
process of welding offers a big economic potential. For welding only a higher beam power is
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applied. The possibilities for the image generation and processing are "built in" anyway and do not
require any extra components for the machine (except intelligent programming).
The electron beam can weld a variety of different or even dissimilar materials. Also reactive
materials are welded with the EB. A little overview is shown in Pic. 5.
Bronze/Steel, 30 mm Aluminium, 40 mm
steel, 150 mm Copper, 35 mm Stainless, 2 mm
Examples of different welds made by EB-process
The electron beam offers the so called deep welding effect. Due to the high energy density onto a
local spot there are advantages in quality and process sequencing. Single pass welding depth for
steel of 100 mm and more are possible, for Aluminium even 200 mm are achieved. The welding
depth limit is mainly given by the power rating of the machine. Welding speed vary according to the
depth and the process requirement between a few mm per second to several 100 mm per second.
3. Fast Beam Deflection and Multi Pool Welding
The electron beam can be deflected by magnetic fields, similar like shown for the scanning of a
work piece shown in picture 2. Due to the limited mass of the electrons the beam can be deflected
with almost no inertia. The possibilities for deflection processes are not limited to image
The electron beam can be deflected very fast using appropriate magnetic coils. Thus welding can
be done at more than one spot. The deflection system must guarantee to be so fast that the beam
returns to each spot after only a few milliseconds to feed more energy into the weld pool.
Metallurgical this does not affect the quality of the weld. Distortion can be positively influenced by
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introducing the welding energy symmetrically over 3 spots, each 120° apart on an axial
weld as shown in picture 6 below.
Rapidly changing magnetic fields controlled fast deflection or focusing coils offer further
applications like online joint detection or per and post heating. By modifying the focus current the
beam can follow changing working distances like in contour changing work pieces of turbines or
Applications for fast beam deflection
Shown are different possibilities for "splitting" the beam to be utilized at multiple pools.
Left: minimizing distortion and increasing productivity
Center and right: productivity increase
4. Applications of EB Welding in Transportation Industry
Demanding tasks for aircraft industry, automotive volume production or safety related components
for the rail industry arise for EB-welding anytime. Besides the small seam, the low energy input and
thus the resulting minimized distortion are the technical key advantages of the electron beam
process. The high welding speeds or even productivity increase by multi pool welding and the
possibility for automated and unmanned joint detection economically convince manufacturers to
apply electron beam welding.
5. Unmanned Welding of Ring of Vanes for Aircrafts
Safety requirements for aviation components call for high standards for the welding process. One
of the most advanced electron beam welding machines is currently used by Rolls-Royce for
welding titanium components of Trent jet engines.
The ring of vanes (ROV) for a front bearing housing is a structural component of a Trent jet engine.
It is assembled from individual vanes and panels which are joined using electron beam welding.
Due to the size and complexity of the part and due to thermal expansion during the welding
process manual positioning of the joints was required in the past.
Key to the automation is a sophisticated scanning process where the joint in between two vanes is
scanned. Because of poor light conditions at the joint the scanning parameter have to be adjusted
during the scan. Result is a sharp and clear image of the joint which is the basis for an automatic
Using the advanced pro-beam seam tracking system the positioning process was automated
resulting in a significant reduction of processing time. At the same time the quality of the welds
could be improved since it no longer depends on the skills of the operator.
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The machine is operated with a HV electron beam generator. A CNC controlled 5 axis mechanical
manipulator positions the part relative to the electron beam. Powerful vacuum equipment
evacuates the process chamber to the process vacuum of 7 x 10-4 within less then 15 minutes.
standard situation contrast contrast and seam detection
Pic 7: Pic. 8
EB welded front bearing housing for Trent 700 Sequence of images of joint scanning process
Universal EB welding chamber type K640 with Trent 700 ring of vanes
6. Optimizing the distortion of work pieces in automotive applications
In automotive industry welding of gear wheels is the largest volume application. This is due to the
fact that finished machined parts can be welded to form ratchet wheels,, input shafts, flange-shafts,
Concerning shrinkage the radial weld shall be prioritized in design as there is no blockage for the
shrinkage. On the other hand axial welding seams have to be applied for design or economic
Usually distortion that comes during cooling is so limited that the final product is within normal
tolerance range. However, harshness is increased due to minimal run out offsets. Therefore even
tighter tolerances for run out are considered by symmetric heat input through multi pool welding.
Besides harshness minimizing also cost are reduced by increased productivity.
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Ratchet wheel, Optimized run out tolerance range by multi pool welding
Left: ratchet wheel Center: Detail of grooved synchronizing ring Right: Simultaneous multi pool welding
7. EB-welding of piston rods for shock absorbers
Welding of piston rods is a demanding task concerning distortion and the safety inspection
Piston rods for shock absorbers
Left: multiple fixture Right: Individual marking by EB-engraving
At the first glance this looks easy. However, the sequence of the individual process steps is quite
critical. High tech cleaning to avoid any porosity in the seam. Proper demagnetizing to prevent
beam deflecting and thus joining imperfections. Precise assembly which is checked by EB-
scanning for tumble. EB-scanning for exact beam positioning, tack welding. Followed by work
piece preheating just locally at the joint to prevent an increase in hardness above tolerance range.
Welding and finally engraving an individual number onto the work piece surface. All process steps
are logically controlled by the CNC and engraving only takes place if all previous process steps
have been completely fulfilled without deviation. Finally a 100% run out check and ultra sonic
testing for welding imperfections is made All data are documented in an integrated data protocol
which guarantees absolute traceability for any individual work piece.
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8. Engine block Cooling Channel
To upgrade the power output of a gasoline engine the diameter of the cylinders has been
increased. Thus the wall between the cylinders of the cast engine block was to thin as to allow for
casting of a cooling channel. Therefore a groove of 0.8 mm width has been milled in the wall
between the cylinders forming the cooling channel. To close the top after machining an Al-sheet
was inserted and EB-welded on both sides with a seam of 8mm depth. The quality of the seams
had to assure the water tightness. The volume production at the OEM was realized by lock-load
Engine block with welded cooling channel
Left: Top view of the engine block Right: Macro cross section of cooling
Lock-Load-Transfer EB Machine for 4 Cylinder Engine Blocks
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9. EB- Welding of Pressure Sensors
Pressure sensors for common rail injection systems require almost contradicting conditions. On the
one hand the welding seam has to be very deep to stand the pressure of about 2.000 bar and on
the other hand the heat input has to be limited not to damage the nearby electronics. The electron
beam could offer the solution by welding a extremely narrow seam with a ratio of depth to width of
12 : 1.
To avoid any out of specification welding the assembled sensors are measured by EB-scanning
just before welding. As these tiny work pieces have a higher risk of tumbling this criterion is
scanned. Only when it is within the allowable range the welding process starts. Otherwise the work
piece will be rechecked for reassembly. Volume production of these sensors is realized on 2 lock-
load-shuttle machines each with 20 spindle fixtures. The cycle time for 20 work pieces is about 90
Pressure Sensor with macro cross section showing the seam connecting 3 dissimilar steel grades
10. Safety Parts for Rail Industry
Rail industry is well known for their high levels of requests in regard to reliability and safety. Such
components are the railcar couplings. For cost reduction purposes the couplings were redesigned
and split into the coupling ring and the housing. This should alow to manufacture all different
varieties from standardized rings and housings. The EB-process has been choosen for the radial
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Two different Railcar coulings
For regular locomotive hooks the design has been changed in the same manner. The hook itself is
forged and the long shaft is made from rolled or longitudinal forged bars. The rectangular cross
section is welded by two EB seams, one from each side.
Top: Completed Hook Bottom: Macro Cross Section
11. EB-Welding of Hightech-Propulsion Systems for Marine Industry
Large towing boats in a harbor are required to rotate on the spot. A core element of this special
drive, the rockers arms are welded by two radial welds each with 30 mm welding depth. To
guarantee a smooth rotation on the fixture counterweights have to be applied. After welding the
seams are 100% ultra sonic tested.
Rocker Arm for Propulsion System
Left: Rocker Arm on Fixture with Counter Weights Right: Towing Boat rotating on the spot
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12. Conclusion and Outlook
After more than 50 years the Electron Beam welding process today is a wide range player in the
industry. For any kind of application there are EB-welding machines available. The reproducible
quality and the excellent economics are main reasons for this process in the transportation
industry. Besides quality the technical advantages of minimal heat input and thus lowest distortion
are often the criteria for electron beam welding. The EB-machines today do cover the full range of
side processes from tack welding over preheating to joint detection and individual part marking,
which is an additional advantage compared to individually sequenced processes. The newer
features like multi pool welding and online quality supervision will further enlarge the range of
applications for the electron beam process.